In the manufacture of many powdered instant food and beverage products, such as instant coffee and tea, instant soups, instant desserts, and the like, the food or beverage components are subjected to heating during processing, which results in the loss or deterioration of volatile compounds which contribute to the desirable aroma and/or flavor of the product which is reconstituted by the consumer. To compensate for such loss during processing, natural and synthetic aromas and flavors, which consist of various combinations of alcohols, aldehydes, ketones, esters, and the like, typically are added to the finished product in an attempt to provide the product with the desired aroma and/or flavor. However, such natural and synthetic aromas and flavors are highly volatile and extremely sensitive to oxidation by atmospheric oxygen and to moisture. As a result, many of these substances, after incorporation in the food or beverage, lose much of their original aroma and flavor and fail to provide the consumer product with the desired characteristics.
For example, in the production of soluble coffee products ground roasted coffee is typically extracted with an aqueous liquid, with the extract being filtered, concentrated by evaporation and converted into powder form by freeze drying or spray drying. One of the major problems with this type of process is the fact that the powdered product obtained lacks the desired aroma of freshly brewed coffee, since the extraction, concentration and drying steps normally utilized in industrial production of soluble coffee products typically result in loss and degradation of volatile aroma constituents.
It has been recognized that the aroma and flavor of soluble coffee products upon reconstitution with a hot aqueous liquid, can be improved by incorporating in the soluble coffee powder aroma compounds which have been evolved during the coffee processing operation. A number of procedures have been proposed heretofore to incorporate volatile coffee aroma compounds in soluble coffee powders. However, none of these prior procedures has been entirely satisfactory since aromatic coffee substances are extremely volatile and unstable. For example, in one proposed method, an aromatic coffee substance is emulsified in water and the emulsion is dropped into finely ground soluble coffee powder which is vibrated and allowed to stand for an appropriate time to coat the aromatic substances with coffee powder. However, the aromatic substance can not be adequately coated so that substantial amounts of the volatile aroma are lost during storage.
In recent years, a number of procedures have been suggested which utilize coffee glass in connection with natural and synthetic aromas. In such procedures coffee aroma typically is dispersed in an extruded matrix of coffee glass. For example, a coffee concentrate having about 88% to 97% total coffee derived solids, is heated to between about 60.degree. C. to 130.degree. C. to provide a viscous melt. Coffee aroma compounds are dispersed in the hot viscous melt, and the resulting melt is then extruded through a restricted orifice into a sheet. Upon cooling, the viscous melt solidifies to a hard glass having coffee aroma dispersed within the glass matrix. The cooled sheets are broken into pieces of a desired size which usually are incorporated into jars of soluble coffee products. Such prior procedures suffer from the disadvantage that the addition of coffee aroma to the hot, liquefied melt of coffee solids prior to extrusion causes considerable thermal degradation of the coffee aroma, which adversely affects the desired aroma profile in the product. Moreover, unless the aroma-containing coffee glass matrix is broken up into relatively fine particles, the rate of dissolution of the coffee glass in hot water is not sufficiently rapid to provide the desired burst of aroma in the cup. Rather, as the coffee glass particles dissolve, the major portion of the aroma dispersed in the glass matrix, is released relatively slowly, and is dissolved in the water without ever leaving the cup. It has been suggested that the solubility of the coffee glass particles may be improved by gasification of the hot viscous coffee melt prior to extrusion. However, such a gasification procedure has not been entirely successful in releasing aroma constituents in a concentration sufficient to produce an aroma which the consumer can immediately sense as above-cup aroma.